1. Field of the Invention
The present invention relates to a technology for controlling an output of a clock signal generated by an oscillator.
2. Description of the Related Art
Conventionally, a hard disk controller (“HDC”) built in a hard disk drive (“HDD”) controls the HDD by using a clock signal output from an oscillator built in the HDD. The HDC starts receiving the clock signal after a predetermined time elapses since a time when a power supply to the HDD is started, and controls the HDD based on the clock signal.
There is a lapse between the time when the power supply to the HDD is started and the clock signal is received by the HDC because the clock signal output by the oscillator immediately after the power supply to the HDD is started tends to be unstable and if the HDC controls the HDD using the unstable clock signal, HDC is likely to malfunction leading to a failure of the HDD.
Japanese Patent Laid-Open Publication No S57-111759 discloses a technology in which when the HDC outputs a write instruction to the HDD, any error in data forwarding is detected by detecting the presence or absence of a write clock output from the HDC.
However, in the conventional technology, in some situations, the clock signals output from the oscillator tend to be unstable even after some time has elapsed since the time the power supply to the HDD is started, and thus is found to be inadequate as a measure against HDD failure.
A method of controlling the HDD by receiving the clock signal after sufficiently delaying the timing at which the HDC retrieves the clock signal output from the oscillator can be considered. However, in this method, the initiation time of the HDD will also get delayed and therefore would not be useful.